Swift NSBundle pathForResource()返回nil

我的项目中有图像(仅在iPhone上支持，而在iPad上不支持).图像在一个组下，而不在images.xcassets下.

I have images in my project (which is only supported on iPhones, no iPads). The images are under a group and not under images.xcassets.

我想在所有iPhone上使用相同的图像，但6 Plus的@ 3x除外，所以我的结构如下:

I want to use the same image for all iPhones, except the @3x for the 6 Plus, so I have a structure as follows:

  Project   
        |_ Images_Group
            |
            |_ pic01@2x.png
            |_ pic01@3x.png

我正在使用以下代码在我的应用中使用它:

I am using this code to use it in my app:

if let path = NSBundle.mainBundle().pathForResource("pic01", ofType: "png") {
            image = UIImage(contentsOfFile: path)
        } 

但是path总是返回nil.我需要pic01.png吗?

But path always returns nil. Do I need to have pic01.png?

该图像位于项目> 构建阶段> 复制捆绑资源下.我在做什么错了?

The image is present under Project > Build Phases > Copy Bundle Resources. What am I doing wrong?